"Chapter 1 - The Op Amp's Place in the World" - HTL Wien 10

2.1 Introduction
Review of Circuit Theory
Ron Mancini
Although this book minimizes math, some algebra is germane to the understanding of
analog electronics. Math and physics are presented here in the manner in which they are
used later, so no practice exercises are given. For example, after the voltage divider rule
is explained, it is used several times in the development of other concepts, and this usage
constitutes practice.
Circuits are a mix of passive and active components. The components are arranged in
a manner that enables them to perform some desired function. The resulting arrangement
of components is called a circuit or sometimes a circuit configuration. The art portion of
analog design is developing the circuit configuration. There are many published circuit
configurations for almost any circuit task, thus all circuit designers need not be artists.
When the design has progressed to the point that a circuit exists, equations must be written
to predict and analyze circuit performance. Textbooks are filled with rigorous methods
for equation writing, and this review of circuit theory does not supplant those textbooks.
But, a few equations are used so often that they should be memorized, and these equations
are considered here.
There are almost as many ways to analyze a circuit as there are electronic engineers, and
if the equations are written correctly, all methods yield the same answer. There are some
simple ways to analyze the circuit without completing unnecessary calculations, and
these methods are illustrated here.
2.2 Laws of Physics
Chapter 2
Ohm’s law is stated as V=IR, and it is fundamental to all electronics. Ohm’s law can be
applied to a single component, to any group of components, or to a complete circuit. When
the current flowing through any portion of a circuit is known, the voltage dropped across
that portion of the circuit is obtained by multiplying the current times the resistance (Equation
2–1).
2-1